I walked into the pilates class to find my nemesis sitting on the floor at the back of the room, planning her next move.

She called me out on two counts: for being late (I was not), and my ‘enormous bottom’ (I’d seen larger).

The stand-in instructor immediately spotted the tension between us and marched us out of the studio. ‘She started it!’ I protested. My nemesis was enjoying this.

Not long afterwards the instructor chased after me. After five minutes alone in the company of my nemesis, she understood the problem. She welcomed me back to her class with an apology. My nemesis was banned from pilates forever.